DE10392854B4 - Method, system and calibration wafer for calibrating temperature measuring devices in heat treatment chambers - Google Patents

Abstract

A method of calibrating a temperature measuring device (27), comprising: radiating light energy from a calibration light source (23) onto a wafer (14) made of a semiconductor material while heating the wafer (14); Detecting the radiated amount of the light energy transmitted through the wafer (14); Determining the temperature of the wafer (14) based on the amount of transmitted light energy being detected; and calibrating the temperature measuring device (27) which measures the temperature of the wafer (14) based on the temperature determined from the amount of light energy transmitted through the wafer (14).

Description

Background of the invention

A heat treatment chamber, as used herein, refers to a device that rapidly heats objects, such as semiconductor wafers. Such devices typically include a substrate holder for holding one or more semiconductor wafers and an energy source for heating the wafers, such as heat lamps and / or electrical resistance heating. During a heat treatment, the semiconductor wafers are heated under controlled conditions according to a predetermined temperature specification.

Many semiconductor heating techniques require that a wafer be heated to high temperatures so that various chemical and physical transformations can occur when fabricating a device from the wafer. For example, in a rapid heat treatment, semiconductor wafers are typically heated to temperatures of about 300 ° C to about 1200 ° C by an array of lamps for periods of time, which are typically less than a few minutes. In these methods, a major goal is to heat the wafers as evenly as possible.

In the rapid heat treatment of a semiconductor wafer, it is desirable to monitor and control the wafer temperature. In particular, it is important for all of the high temperature wafer processes of present and foreseeable interest that the true temperature of the wafer be determined with high accuracy, repeatability and speed. The ability to accurately measure the temperature of a wafer is associated with a direct gain in the quality and size of the integrated circuit produced.

One of the most significant challenges in wafer heating systems is the ability to accurately measure the temperature of substrates during the heating process. Various tools and devices for measuring the temperature of substrates in heat treatment chambers have been developed in the past. Such devices include, for example, pyrometers, thermocouples which directly contact the substrate or which are located adjacent the substrate, and the use of laser interference.

To use pyrometers in a heat treatment chamber, the pyrometers must generally be calibrated. As a result, there are currently various calibration methods to compare the temperature readings of the pyrometers with an absolute and accurate temperature comparison value. The current state of the art and the most commonly used method for calibrating pyrometers in heat treatment chambers is to place in the chambers a semiconductor wafer having a thermocouple embedded in the wafer. The temperature measurements from the thermocouple are compared with the temperature readings obtained from the temperature measuring devices, and any deviation is compensated by calibration.

Although this method is well suited for calibrating temperature measuring devices, such as pyrometers, it requires a considerable amount of time to calibrate the instruments. Therefore, there is currently a need for a method of very rapidly calibrating pyrometers in heat treatment chambers without causing a significant idle time margin. In particular, there is a need for a method of calibrating pyrometers in heat treatment chambers without having to open the chamber in order to maintain the integrity and cleanliness of the chamber. Further, there is a need for a simple method of calibrating pyrometers in heat treatment chambers, which can be routinely used as a regular test to prove that the optical pyrometry system is functioning properly.

From the publication US Pat. No. 6,160,242 A For example, an apparatus and method for determining the temperature of a semiconductor wafer in a processing chamber in the presence of a radiation-absorbing gas is known. The apparatus includes a temperature measuring device that can measure an amount of electromagnetic radiation emitted from the heated wafer. In addition, the device includes a gas measuring device that can measure the amount of gas in the chamber.

From the publication US 6 561 694 B1 For example, a method and apparatus for calibrating temperature measurements is known. The temperature measurements are carried out with a first radiation detector, which receives heat radiation from a reference carrier. According to the method is in one step the reference carrier is heated, on which a reference sample having a known melting point temperature is arranged, to or above the melting point of the reference sample. In addition, during heating, during cooling or during heating and cooling, the heat radiation of the reference carrier is measured. The method further includes the step of comparing a region of constant intensity of heat radiation that occurs in the measurements with the known melting point temperature.

From the publication US 5 156 461 A For example, a pyrometer-based temperature sensor is known for simultaneously measuring the temperature of a semiconductor wafer and compensating for emission effects. The pyrometer measures the radiant energy radiated from the heated semiconductor wafer and the coherent light rays reflected from the semiconductor wafer. From this, the temperature sensor generates high-quality measurements of the semiconductor temperature during production.

Summary of the invention

The present invention relates to a method of calibrating a temperature measuring device in a heat treatment chamber. The method includes the steps of placing a calibration wafer in the heat treatment chamber. Light energy is radiated from a calibration light source onto the calibration wafer while the calibration wafer is heated in the heat treatment chamber. For example, the wafer may be heated using light energy and / or by using electrical resistance heating. The amount of the light energy radiated from the calibration light source, which is transmitted through the calibration wafer, is detected. The temperature of the calibration wafer is then determined based on the amount of transmitted light that is detected.

Based on this information, the temperature measuring device contained in the heat treatment chamber can be calibrated. The temperature measuring device may for example consist of one or more pyrometers, one or more thermocouples or any other suitable temperature measuring device.

During the process, the light energy transmitted through the calibration wafer is detected at one or more particular wavelengths. In general, the wavelength can be in the infrared range. For example, the wavelength may be from about 1 micron to about 2 microns. In one embodiment, transmitted light is detected simultaneously at different wavelengths. However, in an alternative embodiment, a first wavelength is used to detect the amount of light transmitted through the wafer at lower temperatures, while a second wavelength is used to determine the amount of light transmitted through the wafer at higher temperatures , For example, the first wavelength may be smaller than the second wavelength. The second wavelength may be used to determine the temperature of the wafer at temperatures higher than about 700 ° C.

The calibration light source used in the present invention may be a coherent light source or an incoherent light source. An example of a coherent light source is, for example, a laser. Examples of incoherent light sources are, for example, a tungsten halogen lamp or a light-emitting diode.

The calibration wafer used in the method of the present invention may vary, depending on the particular application. In one embodiment, the wafer is a silicon wafer. In order to reduce interference effects and maximize the amount of light transmitted through the calibration wafer, the calibration wafer may include reflection attenuating coatings deposited on one or both surfaces of the wafer. For higher temperature measurements, the calibration wafer may further include thin areas where the transmission measurements are made and the temperature measurement devices are calibrated.

If the calibration wafer comprises a thin area, the thin area can be made according to various methods. For example, in one embodiment, the calibration wafer may define an opening. The thin region may comprise a thin element disposed over the aperture. Alternatively, the thin region may be integrally connected to the remainder of the wafer.

In some embodiments, the thin region may generate temperature gradients when heated due to differences in thermal properties between the thin region and the remainder of the wafer. As a result, a coating can be placed on the calibration wafer, which is suitable to reduce the differences in thermal properties between the thin region and the remainder of the wafer. The coating can be made from single or multi-layered films. The coating may contain, for example, silicon, polysilicon and / or silicon nitride. In a particular embodiment, the thin region may be filled with a filler to reduce mass differences in thermal mass. The filler may be made of quartz or alumina, such as sapphire.

It should be noted that the calibration wafer can be made of different materials. For example, in one embodiment, the calibration wafer may be made of a substantially opaque material. Opaque materials are useful when calibrating pyrometers at lower temperatures. In this embodiment, the calibration wafer may further include regions made of transmissive materials, such as silicon. The silicon regions can be used to measure the transmission while the opaque regions can be aligned with the pyrometers.

Short description of the drawing

A complete and comprehensible disclosure of the present invention, which includes the best mode for practicing thereof, to those skilled in the art, is set forth in detail in the remainder of the specification with reference to the accompanying drawings, in which:

1 Figure 4 is a side view of one embodiment of a system for calibrating temperature sensing devices according to the present invention;

2 is a graph illustrating the amount of light transmitted through a silicon wafer at various temperatures and wavelengths;

3 Figure 4 is a side view of one embodiment of a system made in accordance with the present invention;

4 Figure 3 is a perspective view of an alternative embodiment of a system made in accordance with the present invention;

5 another alternative embodiment of a system made in accordance with the present invention;

the 6 to 21 illustrate various embodiments of calibration wafers made in accordance with the present invention; and

22 Fig. 12 is a schematic cross-sectional view illustrating multiple reflections of light between the outer surfaces of a wafer.

Repeated use of reference signs in the present specification and drawings is intended to represent the same or analogous features or elements of the invention.

Detailed description of the preferred embodiments

The present invention relates to a method and system for more accurately determining and controlling the temperature of an article, in particular a semiconductor wafer, in a heat treatment chamber during a heat treatment. More particularly, the present invention relates to a method and system for calibrating temperature measuring devices contained in heat treatment chambers so that the heat treatment chamber operates in a more repeatable and accurate manner. For example, it is important that temperature sensing devices included in heat treatment chambers accurately measure the temperature of semiconductor wafers as they are heated. In view of this, the temperature sensing devices should be calibrated to ensure that they closely track the temperature of the wafer.

Generally, the method of the present invention for calibrating temperature sensing devices, particularly radiation sensing devices, such as pyrometers, includes the step of placing a calibration wafer in a heat treatment chamber. A calibration light source, which is arranged in the chamber is adapted to radiate light energy of a known wavelength on the wafer. On the opposite side of the wafer, a light detector is arranged, which detects the amount of light from the calibration light source, which is transmitted through the wafer. This information is used to calibrate a temperature sensing device contained within the chamber used during normal wafer processing.

The present invention enables automatic calibration of a temperature measurement system by an automated process performed with a semiconductor wafer processing system. The temperature calibration method is based on a local measurement of the transmission of infrared light through the semiconductor wafer. The wafer processing apparatus includes both a device for measuring a signal coming from the infrared light transmitted through the wafer, and a temperature measuring system, such as a pyrometer system, used in a normal temperature measurement and control process. Known knowledge about the temperature dependence of the optical properties of the wafer used for the calibration process is combined with the measured infrared transmission signal to derive the wafer temperature. The wafer temperature is used to calibrate a pyrometer system or other temperature measuring device.

The intensity of a light source on one side of a calibration wafer is modulated, and a detector on the opposite side detects a signal which is proportional to the amount of light transmitted through the wafer. The system includes a method for selecting the wavelength of the observed radiation. The transmitted signal depends on the optical absorption in the wafer, which is a function of temperature. As a result, the wafer temperature can be derived from the transmitted light signal.

The infrared transmission measurement is tuned to occur at a position on the wafer that is in the field of view or near the field of view (within a few centimeters) of the pyrometer or other temperature measuring device. Further, if the system permits wafer rotation, it is possible for the infrared transmission measurement to be performed at the same radius or near the same radius as that of the field of view of the pyrometer or temperature device being calibrated. Provided that the wafer rotation occurs at a speed fast enough to produce an angularly symmetric temperature distribution, the temperature measured in the infrared measurement is the same as that received by the pyrometer at the same particular radius. In one embodiment, the same fiber (s) leading to the light detector for determining the amount of infrared light transmitted through the wafer may lead to the pyrometer, such as by optically splitting the signal.

Calibration of the temperature measuring device may be accomplished by an automated process, with wafers automatically inserted and a calibration protocol heating the wafer in a prescribed temperature-time cycle and collecting data through the infrared transmission system and the pyrometer system. The process may include a step on which the measurement is taken, the wafer being at a temperature at which its permeability is known and it is not very temperature sensitive. This allows the signal to be corrected so that the transmission measurement is not very sensitive to changes in the optical properties of the transmission measurement system or the calibration wafer.

The transmission signal is interpreted as temperature by an algorithm which takes into account the properties of the wafer used for the calibration. The algorithm can capture information about the thickness of the wafer, the wavelength of light used for calibration, and other parameters that help increase the accuracy of the temperature value derived from the transmission signal.

The method for calibrating the temperature measuring devices may further comprise a step in which measurements using the transmission system take place before a wafer is placed in the heat treatment chamber. The ratio of the transmission signal to a wafer in position compared to that without wafer provides an estimate of the transmissivity of the wafer. The measured transmittance of the wafer can then be used to ensure that a proper wafer has been loaded and to test for the deterioration of the wafer. The transmission signal level when there is no wafer is also a useful indicator of the state of the optical system for transmission measurements.

The method and system of the present invention offer several advantages and benefits. For example, the present invention provides a relatively simple method for rapidly calibrating the radiation sensing devices. The calibrations may, if desired, be performed automatically by placing a calibration wafer in the heat treatment chamber between wafers or wafer groups. Further, a calibration wafer may be inserted and removed from the heat treatment chamber using the same apparatus that moves and conveys the wafers.

The present invention enables the calibration of radiation detectors in heat treatment chambers according to a relatively simple process which does not require significant disturbance of the operation of the chamber. The present invention can be used to calibrate one or more point pyrometric systems. Further, the method and system of the present invention allow for calibration without having to accommodate a thermocoupled wafer as in the past.

In 3 Now, an embodiment in the form of a simplified schematic representation of the present invention is shown. As shown, the system comprises a semiconductor wafer 14 and a temperature measuring device 27 , such as a pyrometer, which is normally used to monitor the temperature of the wafer. To the temperature measuring device 27 To calibrate, the system further includes a calibration light source 23 , which at a certain place infrared light on the wafer 14 radiates. On the opposite side of the wafer is a light detector 42 , which detects the amount of infrared light passing through the wafer 14 is allowed through.

Measurements of the transmissivity of the wafer can be used to determine the temperature since the absorption coefficient α (λ, T) of silicon is a function of the wavelength λ of the radiation and the temperature T. The following discussion includes the mathematical principles that link the transmission measurements to α (λ, T).

A general wafer has various properties to be considered. The two surfaces of the wafer may have different reflectance values and transmission values. Further, the reflectance values of the surfaces for radiation striking them from outside the wafer or from within the wafer may be different. When a wafer is semi-transparent, multiple reflections of the various energy beams traveling in the wafer, its apparent reflectivity R x (λ, T), and its apparent transmission S x (λ, T), as viewed from outside the wafer. The latter quantities can be measured directly by optical measurements. In the calibration method, S x (λ, T) can be measured since this size is the most temperature sensitive (although R x (λ, T) can also be used for temperature measurements). In some documents, R x (λ, T) is referred to as the reflection value and S x (λ, T) as the transmittance value.

In the discussion below, T _{t is} the transmittance of the upper surface of the wafer, T _b is the transmittance of the lower surface of the wafer, R _ts is the reflectivity of the upper surface of the wafer for radiation incident upon it from within the substrate, and R _bs is the reflectivity of the lower surface of the wafer for radiation which strikes it from within the substrate. In general, if the incident radiation is not normal, all the properties are functions of the plane of polarization of the radiation. The quantity A is the intensity attenuation of a beam passing through the substrate given by A = exp (-α (λ, T) d / cos θ) (1)

Where d is the thickness of the substrate and θ is the inner running direction angle. The latter angle is the angle of the direction of the beam and the perpendicular to the wafer surface. The apparent transmissivity of the wafer is then given by the term

The signal measured at the photodetector V (T) in the device is directly proportional to this magnitude and to the intensity of the radiation _incident on the wafer from the illumination light source I ₀ . The relationship is V (T) = CI ₀ S · (λ, T) (3)

• (a) Normieren bezüglich des Falls, daß der Wafer nicht in dem System vorhanden ist: In diesem Fall wird der Durchlässigkeitswert des Systems 1, da kein Wafer vorhanden ist, um Strahlung zu absorbieren oder zu reflektieren. Es kann ein Normierungssignal V₀₀ gemessen werden, welches gegeben ist durch V₀₀ = CI₀ (4)

Where C is a constant which is affected by the optical and electronic devices, but which does not change with the wafer temperature. To derive the wafer temperature, the effects of the unknown quantities comprising I ₀ and C should be eliminated from the measurements. This can be done in several ways. The optical properties of the wafer surfaces (such as their reflection and transmission values) should also be considered. A "standardization procedure" can take these aspects into account. For example, two approaches are described below:

• (a) normalizing with respect to the case that the wafer is not present in the system: in this case, the transmittance value of the system becomes 1 because there is no wafer to absorb or reflect radiation. It can be measured a normalization signal V ₀₀ , which is given by V ₀₀ = CI ₀ (4)

By dividing a signal V (T) of a "hot wafer" by V ₀₀ , the effects of C and I ₀ can be eliminated. However, the effects of the other quantities in S · (λ, T) still need to be considered. This can be done by knowing the optical properties of the wafer used, which includes T _t , T _b , R _bs and R _ts . In view of this, the wafer used in the calibration process can be selected such that these quantities can be determined by performing calculations based on the known film coatings on the surfaces of the wafer. The calculations can be further extended by various optical measurements which can be made under controlled conditions. The absorption coefficient can then be obtained by solving for A in Equation 1 from the measured value of S · (λ, T). If A is known, it is possible to make a correction for the effect of the wafer thickness (which has been measured) and derive α (λ, T). Since the function α (λ, T) is known, T can be derived. This process also makes it possible to make corrections for changes in the wavelength of the light source. The exact method of implementing this procedure may vary depending on the application. For example, as an example, one may generate a matrix group for S · (λ, T) with wafer thickness and source wavelength as parameters and T as a variable, and then numerically determine an optimum value for T in accordance with the measured value of S · (λ, T) ,

The variables T _t , T _b , R _bs and R _ts may in turn have temperature and wavelength dependencies. For the sake of accuracy, this effect should be taken into account in the analytical evaluation by explicitly including the known behavior of the wafer surfaces. Again, the corrections are possible by using standard optical methods of analytical evaluation to calculate T _t , T _b , R _bs and R _ts as functions of wavelength and temperature.

(b) normalizing with respect to the case that the wafer is in a "cool" state:
In this case, the normalization signal V _{01 is} recorded after the calibration wafer is inserted into the system. V ₀₁ is given by V ₀₁ = CI ₀ S · (λ, T _cool ) (5) where S · (λ, T _cool ) is the wafer permeability at the "cool" temperature. This temperature is normally any temperature at which the absorption in the wafer at the calibration wavelength is negligible. In this case A ≈ 1, and you can write:

Now, if a signal V (T) of a "hot wafer" is normalized using V ₀₁ , the expression is obtained

Provided that T _t and T _b do not depend on the temperature, this then simplifies

vorausgesetzt, daß R_tsR_bs << 1 ist, kann sich der Ausdruck weiter vereinfachen zu

Further simplification may be made by checking the magnitude of the product A ² R _ts R _bs appearing in expression 8. This term is usually very small for two reasons. First, for a good temperature sensitivity, there must be a reasonably strong absorption in the wafer, so A should be well below 1. Second, a wafer can be selected which has relatively small values of reflectivity of the wafer surface at the transmission measurement wavelength. This can be done to maximize the transmitted light signal. Another practically significant issue is that the interference effect observed when coherent light sources are used for illumination causes some problems in the measurements. By having a very small value for R _ts or R _bs , the above problems can be alleviated. Furthermore, even for a simple silicon wafer, R _ts = R _bs ≈ 0.3, that is, R _ts R _bs ≈ 0.09. Thus, the term R _ts R _{bs is} usually << 1. As a result, one can make the approximation of neglecting this term compared to 1 in the denominator of Expression 8. This simplification results in a simple form for the signal when normalized with respect to the "cool" state

provided that R _ts R _bs << 1, the expression can be further simplified

The advantage of this approach is that, given that there is no significant temperature dependence at T _t or T _b , it is not necessary to know the optical properties of the wafer surfaces. This can make the temperature interpretation less sensitive to changes in the properties of coatings on the wafer and the fine structure of the surfaces.

The question of which standardization approach is better is determined by practical considerations. The advantage of the case that the measurement is made without the wafer being present is that one need not fear any interference effects which have their strongest influence in the "cold" state. The advantage of making the measurement while the wafer is in the "cool" state is that it automatically compensates for any small variations in surface reflectance, transmittance, or fine-structure effects.

The above-described analytical evaluation is entirely based on the premise that the apparent reflectance and the apparent transmissivity can be calculated by adding up the energy contributions produced by the various beams which undergo multiple reflections, which in 22 are shown. This assumption is valid if there is no correlation between the electric fields associated with these rays. This is the case when the detected radiation comprises an optical bandwidth which represents a significant fraction (eg> 0.001) of the "midpoint wavelength" and the wafer is "optically thick", that is to say its thickness is a large multiple (for example> 100 times) corresponds to the wavelength of the light. These conditions correspond to the case where the light is considered to be "incoherent".

In the case that the light source is "coherent", the radiation that is detected typically includes a very narrow range of wavelengths and / or the wafer is optically "thin". In this case, there may be a strong correlation between the electric fields of the various beams passing in the wafer. If this is the case, adding the energy contributions will not reflect the correct physical conditions. Instead, it is necessary to make a vectorial summation of the electric and magnetic fields of the electromagnetic waves associated with the rays which undergo multiple reflections to obtain the proper apparent reflectance and transmittance values. Under these conditions, the effect of the phase changes of the waves as they traverse the substrate becomes very important. When the fields for two wave components are added in phase, the effect is known as constructive interference, since the resulting field is amplified, and if these are exactly out of phase, this is known as destructive interference, because the resulting field is weakened. These interference effects can exert a stronger influence on the optical properties and also make them extremely sensitive to the phase change that occurs and therefore to the wafer thickness, the wavelength of the radiation, the angle of incidence and the refractive index of the substrate.

This can be a problem since this is associated with very large fluctuations in the detected signals which are not associated with changes in α (λ, T), the absorption coefficient of silicon. The problem is greatly diminished as the absorption increases and the wafer becomes opaque, since the multiple reflections are strongly attenuated and most of the transmitted light intensity is mainly due to the light passing directly through the substrate, so that interference effects exert little influence , Hereinafter, various methods of reducing problems caused by interference effects will be described.

From the ratio of the irradiation of a wafer at a relatively high temperature to the transmission, if the absorption is negligible (see the equations above), such as at low temperatures or if there is no wafer in the system, the temperature of the wafer may vary higher temperatures are calculated. For example 2 FIG. 12 is a graph illustrating the transmittance ratio measured for a silicon wafer having a diameter of 200 mm and a thickness of about 725 microns at various wavelengths. As shown, the wavelengths change from 1.064 microns to 1.55 microns. As also shown, the transmissivity at the longer wavelengths can be used to determine higher temperatures.

At the included wavelengths of light, however, temperature measurements above about 850 ° C become difficult because the transmitted light signal becomes weak and difficult to detect. To make temperature measurements even at higher temperatures, a calibration wafer thinner than the 725 micron wafer used to obtain the results in FIG 2 to create. The use of thinner wafers to determine temperatures in excess of 850 ° C will be discussed in more detail below.

wobei k_Si die Wärmeleitfähigkeit von Silizium ist, d_w die Waferdicke ist, ε_f und ε_b die Gesamtemissionswerte der vorderen bzw. der hinteren Oberfläche sind, σ die Stefan-Boltzmann-Konstante ist und T die Wafertemperatur ist.When the temperature measuring device 27 calibrated as in 3 it is desirable that the calibration light source 23 and the light detector 42 Make measurements as close as possible to the location on the wafer where the temperature through the temperature measuring device 27 is measured. In other words, the calibration probe should be at a position in the field of view of the pyrometer or close enough to have very small temperature differences between the temperature at the calibration probe and the temperature in the field of view of the pyrometer. This can be quantified by using the thermal diffusion length L _d given by:

where k _{Si is} the thermal conductivity of silicon, d _{w is} the wafer thickness, ε _f and ε _{b are} the total emission values of the front and back surfaces, σ is the Stefan-Boltzmann constant, and T is the wafer temperature.

For many applications, the calibration point should be within a range of ≈ L _d around the field of view of the pyrometer. As the temperature increases, the distance becomes smaller. For example, this distance may be small at high temperatures, such as more than 1100 ° C, for example, about 4 mm. However, for many applications, the distance between the calibration point and the pyrometer field of view should not exceed about 3L _d . For example, the distance between the location on the wafer where the temperature is measured by the temperature measuring device and the location on the wafer where the light detector detects the transmitted light should not be greater than about 5 cm in most applications.

When the wafer is rotated in the heat treatment chamber, the accuracy can be maintained by allowing the transmitted light to be at the same or near the same radius of the wafer as that at which the temperature measuring device 27 the wafer temperature is measured, detected as in 4 shown.

In 1 is an embodiment of a heat treatment system, in general 10 , which comprises a system for calibrating temperature sensing devices according to the present invention.

The system 10 includes a treatment chamber 12 , which is suitable to receive substrates, such as semiconductor wafers, to perform various methods. The chamber 12 is capable of heating the wafers at very fast speeds and under carefully controlled conditions. The chamber 12 may be made of various materials, including certain metals, glasses and ceramics. For example, the chamber 12 be made of stainless steel or quartz.

If the chamber 12 is made of a thermally conductive material, the chamber preferably comprises a cooling system. For example, as in 1 represented the chamber 12 a cooling line 16 , which is wound around the circumference of the chamber. The administration 16 is suitable for directing a cooling fluid, such as water, which is used around the walls of the chamber 12 to keep at a constant temperature.

The chamber 12 may also have a gas inlet 18 and a gas outlet 20 for introducing a gas into the chamber and / or for holding the chamber in a predetermined pressure range. For example, a gas may react with the wafers through the gas inlet 18 in the chamber 12 be initiated. After treatment, the gas can then be removed using the gas outlet 20 be pumped out of the chamber.

Alternatively, an inert gas may pass through the gas inlet 18 in the chamber 12 are fed to prevent unwanted or undesirable side reactions take place in the chamber. In a further embodiment, a gas inlet 18 and a gas outlet 20 used to the chamber 12 to put pressure on. Furthermore, a negative pressure in the chamber 12 be generated, if desired, wherein the gas outlet 20 or an additional larger outlet located below the level of the wafer.

During a treatment, the chamber 12 in one embodiment, a substrate holder 15 which is suitable to wafer using a wafer turning device 21 to rotate, as shown by the arrow, which is above the wafer 14 located. The spinning of the wafer promotes greater uniformity of temperature on the surface of the wafer and promotes improved contact between the wafer and any gases introduced into the chamber. It should be noted, however, that the chamber 12 besides being suitable for wafers, also for treating optical elements, films, fibers, tapes and other substrates of any shape.

A heat source, generally 22 , is in communication with the chamber 12 for heating the wafers during treatment. In this embodiment, the heat source comprises 22 a variety of lamps or light sources 24 such as tungsten halogen lamps. The heat source 22 may include a reflector or group of reflectors to carefully direct heat energy radiated to the wafers by the heat source to produce a very uniform wafer temperature. As in 1 shown, are the lamps 24 arranged above the chamber. It should be noted, however, that the lamps 24 may be located at any particular location, such as under the wafer, alone or in combination with lamps 24 ,

The use of lamps 24 as a heat source 22 can offer several advantages. For example, lamps have much higher heating and cooling rates than other heating devices, such as electrical elements or conventional ovens. The lamps 24 produce a fast isothermal treatment system which provides instantaneous energy and typically requires a very short and well-controlled start-up period. The energy flow from the lamps 24 can be abruptly interrupted at any time. As shown in the figure, the lamps are 24 with a gradual energy regulator 25 which can be used to increase or decrease the heat energy emitted by the lamps.

Except for use of lamps 24 or in addition to use of lamps 24 as a heat source 22 can the system 10 a heated susceptor 26 for heating the wafer 14 include. The susceptor 26 For example, it may be an electrical resistance heater or an induction heater. In the system, which is in 1 is shown is the susceptor 26 under the wafer 14 arranged. Similar to the heating lamps, the susceptor 26 however, can also be placed under the wafer, above the Wafer may be arranged or the system may comprise a plurality of susceptors, which are arranged above and below the wafer.

Further, in the chamber 12 a variety of radiation sensing devices, generally 27 , contain. The radiation detection devices 27 include optical fibers 28 , which in turn in conjunction with a plurality of corresponding light detectors 30 are located. The optical fibers 28 are adapted to receive heat energy emitted by a wafer present in the chamber at a certain wavelength. The amount of detected radiation then becomes light detectors 30 which generate a usable voltage signal for determining the temperature of the wafer. In one embodiment, each optical fiber comprises 28 , which in conjunction with a light detector 30 located, a pyrometer.

As shown, the system includes 10 a window 32 which the lamps 24 from the chamber 12 separates. In the illustrated embodiment, the window is used 32 to insulate the lamps 24 from the wafers and to prevent contamination of the chamber.

As in 1 illustrated, the system includes 10 according to the present invention, a calibration light source 23 and a light detector 42 to the radiation detection devices 27 to calibrate. As described above, the calibration light source emits 23 at a certain location, light energy, especially infrared light energy, onto the wafer. That from the calibration light source 23 radiated light transmitted through the wafer is passed through the light detector 42 detected. Based on this information, the temperature of the wafer can be determined to calibrate the radiation sensing device.

As in 1 shown, the calibration light source 23 between the heating lamps 24 directly opposite the wafer 14 be arranged. Alternatively, the calibration light source 23 however, be located at a different location from the chamber. In this embodiment, light emitted from the calibration light source can be supplied to the wafer using fiber optic devices 14 be directed.

To accurately measure the amount of light energy transmitted through the wafer, the detector can 42 a light channel 44 which directs the transmitted light to the light detector, as in 1 shown.

The calibration light source 23 which is used in the system of the present invention may generally be any device capable of emitting light energy at a desired wavelength. For example, the calibration light source 23 an incoherent light source or a coherent light source. Examples of incoherent light sources include tungsten halogen lamps, arc lamps, light-emitting diodes, super-luminescent LEDs, etc. In contrast, coherent light sources include a solid-state device such as a laser diode, a superfluorescent fiber laser, other types of lasers, etc.

When it is necessary to calibrate the radiation detectors, a calibration wafer is formed 14 placed in the chamber, and the above process is carried out. In 1 are just a single calibration light source 23 and a light detector 42 shown. It should be noted, however, that for most applications, the system includes multiple light detectors and corresponding calibration light source for calibrating the various radiation detectors.

In 1 includes the system 10 furthermore a system control 50 which may be a microprocessor, for example. The control 50 receives voltage signals from light detectors 30 representing the amounts of radiation measured at the various locations. Based on the received signals, the controller 50 suitably configured to calculate the temperature of the wafers contained in the chamber.

The system control 50 as shown in 1 can also be used in conjunction with a lamp energy regulator 25 are located. In this arrangement, the controller 50 calculate the temperature of a wafer and, based on the calculated information, calculate the amount of heat energy passing through the lamps 24 is emitted. In this way, immediate adjustments can be made concerning the conditions in the reactor 12 to treat the wafer within carefully coordinated limits. As described above, the system can be used in addition to the lamps 24 or as an alternative to the lamps 24 also a susceptor 26 include, as in 1 shown. In this embodiment can the controller 50 can also be used to control the amount of heat which is emitted by the susceptor. If both heaters are present, the susceptor can be controlled independently of the lamps or in conjunction with the lamps. (Or the system may not contain any bulbs, just a susceptor.)

In one embodiment, the controller may 50 can also be used to automatically control other elements in the system. For example, the controller 50 used to control the flow rate of gases passing through the gas inlet 18 in the chamber 12 enter. As shown, the controller can 50 can also be used to control the speed at which the wafer 14 is turned in the chamber.

According to the present invention, the system controller 50 can also be used to the radiation detection devices 27 to calibrate. For example, the controller may be 50 also in conjunction with the calibration light source 23 and the light detector 42 are located. In this way, the controller 50 used to control when the calibration light source 23 Light radiates and what amount of light is emitted. The control 50 Further, it may be configured to receive information from the light detector 42 to determine the temperature of a calibration wafer and then the radiation detectors 27 to calibrate based on the determined temperature.

Various embodiments of the present invention will now be discussed. In particular, a first mode of operation of the present invention will be described using an incoherent light source, followed by a discussion of using a coherent light source. Thereafter, various embodiments of a calibration wafer will be described. Lastly, methods for carrying out the present invention will be discussed.

Calibration light source

A. Incoherent light source

As mentioned, the calibration light source 23 in one embodiment, be an incoherent lamp, such as a tungsten halogen lamp or a light emitting diode. For example, in one embodiment, the calibration light source may be a super-luminescent light emitting diode. Some incoherent light sources have the advantage that they can be used as a light source for transmission measurements at different wavelengths, as desired. For example, some incoherent light sources emit a wide range of wavelengths while others, such as light emitting diodes, emit relatively narrow wavelength ranges. If an incoherent lamp is used, the light detector can 42 comprise a single detector for detecting a single wavelength or may comprise a detector arrangement which measures the transmitted signal simultaneously at different wavelengths.

It is further noted that except for incorporating a single calibration light source 23 , as in 1 As shown, multiple light sources may be present in the system of the present invention. Alternatively, a single calibration light source may be used which is arranged in conjunction with a plurality of optical fibers for directing the light onto the wafer at a plurality of positions.

In one embodiment, the radiation of the calibration light source may be pulsed, for example by a mechanical chopper, or it may be electronically pulsed. The irradiation of the light energy from the calibration light source onto the wafer at intervals may help determine the amount of background scattered light present by taking a measurement when the calibration light source emits light and when the calibration light source does not emit light.

An embodiment of a system according to the present invention using an incoherent light source as the calibration light source 23 is manufactured in is 5 shown. In this embodiment, the light source transmits 23 a light beam passing through a light detector 42 is detected by a calibration wafer 14 , The light detector 42 For example, it may be a photodetector or any other suitable device.

In this embodiment, the lamp 23 in conjunction with an optical collimation device 60 for focusing the light to a specific location of the wafer 14 used. In order to measure the light transmitted through the wafer and to eliminate stray light, the system may have one or more openings 62 which provide the field of view for the light detector 42 define. One spectral 64 may be further included to better define the wavelength range to be detected. Although the embodiment which is in 5 has been described in connection with the use of an incoherent light source, it should be noted that the use of an optical collimating device and in general of the arrangement which in 5 irrespective of whether the light sources are coherent or incoherent.

B. Coherent light sources

As an alternative to using an incoherent light source, the calibration light source may further be a coherent light source, such as a laser, which can provide relatively high energy in a narrow wavelength range. A specific example of a coherent light source is a semiconductor laser. Such light sources are easy to modulate electrically. Coherent light sources, such as lasers, have a very narrow energy emission spectrum. While this may offer some advantages, the presence of a narrow emission spectrum can also create potential problems. In particular, the system may become more sensitive to interference effects when light emitted by the coherent light source is reflected between the two surfaces of the wafer. In particular, the transmitted signal, which finally the light detector 42 achieved, more sensitive to the wafer thickness and its refractive index than when using an incoherent light source. However, various measures can be taken to counteract this effect.

For example, in one embodiment, a coherent light source may be used that has multiple wavelength emission spectra or a set of narrow emission spectra. In another embodiment, the calibration wafer may include at least one rough surface, although this may have the undesirable effect of scattering some of the light from the light source. In another embodiment of the present invention, the path length of the light emitted by the calibration light source may be changed, for example, by making small changes in the wafer thickness. Specifically, the thickness of the wafer may be changed by, for example, stepwise shrinking in the areas where the transmission measurements are to be made. In another embodiment, the calibration wafer may include reflection-damping coatings, as described in more detail below.

When the wafer is rotated upon heating, it is possible to use the rotation to reduce the effect of interference in the wafer. One approach is to rotate the wafer and measure the transmitted light signal. As the wafer rotates, the thickness of the wafer which is inspected by the infrared ray slightly changes, and the condition for interference changes, causing variations in the transmitted light intensity. By picking up the signal for at least one spin, the effect of the interference can be eliminated by averaging to obtain a more reliable transmittance value.

Another approach is to arrange an optical element (such as a ground glass sheet) in the path of the coherent light source so that the spatial coherence of the light beam is lost. By altering the phase of the oscillations of the electromagnetic field in the cross-sectional profile of the beam and then intercepting a portion of the beam at the detector in such a way that the various components in the measurement signal are combined, the effect of the interference in the wafer or optical elements are greatly reduced. The use of multiple laser sources placed close to each other so that they can be combined to form an optical beam would also achieve similar results. Large area emission sources comprising multiple laser elements may be useful in this embodiment.

In another embodiment, the use of multiple coherent light sources may help to reduce the temporal coherence of the beam by introducing a range of wavelengths. For example, some types of diode lasers do not have a strictly specific emission wavelength. The natural dispersion of device characteristics may result in a wider effective spectrum for illumination. If desired, light devices may be intentionally selected to provide a wider range of wavelengths. Further, some light sources having the same denominations may be purposely operated at different temperatures to produce a range of wavelengths because the emission wavelength is sensitive to device temperature in many cases.

In another embodiment, interference effects may be reduced by using the combination of an incoherent light source and a coherent light source. In this embodiment, the incoherent light source may be used at lower temperatures than the calibration light source. At lower temperatures, transmission measurements do not depend on various parameters, such as the refractive index and the thickness of the substrate. Relatively lower temperatures may include temperatures of less than about 700 ° C, and more specifically less than about 500 ° C.

At relatively high temperatures, such as greater than about 500 ° C, and especially greater than about 700 ° C, the calibration light source may be a coherent light source. At higher temperatures, coherent light sources may be preferred because they provide more energy at a particular wavelength and better wavelength definition. The same or different detectors can be used to detect the transmission from the calibration light sources. These transmission measurements can then be used to detect the transmission from the calibration light sources. For example, in this embodiment, transmission measurements may be made at lower temperatures using an incoherent light source. These transmission measurements can then be used to determine the temperature of the wafer at higher temperatures in conjunction with transmission measurements made using the coherent light source.

Regardless of whether a coherent or incoherent light source is used, it is desirable for most applications that the power supply for the light source be properly designed to provide a stable and repeatable intensity. Although the technique of the present invention is self-calibrating in the sense that the transmissivity measurements when the wafer is hot are made relative to a transmission value obtained when the wafer is at a temperature at which its permeability is known Furthermore, the possibility of a change tendency of the light source intensity, while the wafer is heated according to the calibration rule. This change can be reduced by ensuring that the power supply to the light source is stable. Optionally, an optical detector may be used to measure a portion of the light emitted by the calibration light source and therefore a signal to monitor the light source or to appropriately control the intensity thereof so that it is stable and repeatable during the measurements, to create.

calibration wavelength

The working wavelength for the transmission measurement should be selected with a view to providing good temperature sensitivity. Generally, the wafer should be sufficiently transparent to allow accurate measurement of the transmitted infrared signal intensity. In most situations this requires the transmission at the test wavelength to be greater than 10 ^-6 .

The wafer permeability should also be sensitive to the wafer temperature. For example, it is desirable that the wafer permeability change by more than 0.5% from the value thereof near the particular calibration temperature when changed by 1 ° C. Ideally, the permeability changes by more than about 5% with a temperature change of 1 ° C.

For some applications, it may be advantageous if the calibration wafer is nearly opaque at the pyrometer wavelength while still transmitting a measurable amount of radiation at the transmission test wavelength. This may be desirable for the calibration to correspond to a typical state of optical properties of a standard thickness wafer at the calibration temperature of interest. In practice, it is sufficient if the wafer at the pyrometer wavelength has a transmittance of less than about 0.01, while the transmittance at the wavelength of the infrared transmittance test is greater than about 10 ^-6 . This condition can often be satisfied because the absorption coefficient of silicon typically has a minimum value in the near infrared range, so that the transmission measurement in this wavelength range can be performed under conditions where the wafer is opaque at other wavelengths. This concept may be especially useful for calibration at temperatures above 800 ° C, with standard thickness wafers typically being highly opaque at optical and infrared wavelengths.

In other applications, it may be desirable to know the wavelength of the measurement with a higher accuracy than the nominal value given for an emission source or an optical filter. In this case, the spectrum of the emission source or the permeability of the optical filter are measured, so that the exact measurement wavelength is determined. This value can then be used to improve the accuracy or repeatability of measurements. For example, when the measurement system is used in multiple treatment systems, it may be important to correct for the effect of changes in measurement wavelengths between the systems to achieve the most consistent calibrations in various systems. One way to accomplish this is to use an algorithm that accounts for wavelength input and wavelength changes when a transmitted light signal is converted to a derived temperature.

In one embodiment, as noted above, the system of the present invention may be configured to perform temperature measurements in a range of wavelengths rather than a single wavelength. Measuring the temperature at different wavelengths can offer several advantages. For example, measurement of a transmission spectrum enables the wafer temperature to be determined without having to perform the normalization step of measuring the transmitted intensity at a temperature at which the wafer permeability is known, such as when the wafer is cool. It is possible to determine the temperature since the shape of the absorption spectrum can be determined and used to determine the wafer temperature. In this way it is not necessary to measure the temperature if the permeability is not a strongly temperature dependent function.

More specifically, by measuring the transmittance for at least two wavelengths, a relative transmission at these wavelengths can be defined. The broader spectrum (that is, with multiple wavelengths) can be picked up and fitted to a model using temperature as a parameter for fitting. In this embodiment, there may be advantages and greater flexibility against variations in wafer thickness or unexpected changes in other parameters such as coatings, etc.

These circumstances may also be useful when attempting to calibrate a pyrometer for very low temperature operation, such as less than 200 ° C. Under these circumstances, the normalization temperature typically must be very close to room temperature to prevent the permeability from being sensitive to the exact value of the normalization temperature. This is particularly useful in applications where the heat treatment environment is already warm when the wafer is added, making it very difficult to measure temperatures below about 30 ° C.

Spectral measurements made in a range of wavelengths also tend to make the temperature measurement less sensitive to a change tendency of the light source intensity or detector characteristics, optical noise and noise. Spectral measurements can be made using an incoherent light source that emits light at different wavelengths, or can be done by using multiple light sources, such as multiple incoherent sources or multiple coherent sources. The measurement can be made at the same time or at different times, say one after the other, at different sources.

As in 1 is the calibration light source 23 directly above the light detector 42 arranged. The light coming from the calibration light source 23 may be suitably tuned to fall directly onto the wafer, or alternatively may fall onto the wafer at a non-perpendicular angle of incidence. In some applications, it may be desirable for the light to strike the wafer at an angle to reduce reflection at the wafer surface. For example, when the light is in the P-polarization plane and incident at an angle near the critical angle, the reflectance of the surface approaches zero. Reducing the reflectivity not only allows a stronger signal to pass through the wafer, but also reduces interference effects in the wafer. In one embodiment, it may be desirable to use polarized light with a non-perpendicular angle of incidence.

Reducing the effects of scattered radiation

As described above, in order to improve the accuracy, the measurement and the system of the present invention should be able to distinguish between the transmitted light signal and signals that may be generated by scattered radiation sources. In the embodiment, which is in 1 is shown, the wafer 14 heated only from one side. In this case, the wafer works even as a shield to reduce the possibility of stray light from the light detector 42 achieved because the detector is disposed on a side of the wafer, which is opposite to the light sources 24 located. However, various other ways are available to reduce stray light and interference, particularly for use in systems that contain light sources on both sides of the wafer.

Generally, the calibration light source should be 23 be modulated for most applications such that the light signal transmitted through the light detector 42 is an alternating signal or other similar signal which can be distinguished from signals resulting from stray light originating from the wafer, lamps or other radiation sources. The transmitted light signal may be extracted from the detected signal to eliminate stray light by a variety of techniques, including, for example, spectral filtering, signal averaging, and lock-in amplifier phase-sensitive detection. The above approaches can extract a very weak alternating signal even in cases where the signals are mixed with strong noise components.

In one embodiment, the optical illumination device may also be suitably tuned to maximize the amount of transmitted light that the light detector 42 reached. For example, as in 5 shown, the beam of light passing through the calibration light source 23 is emitted, collimated. Another approach is to use a light source that has a filament temperature that is substantially warmer than the wafer, such as by using a tungsten filament, so that the light source at the monitored wavelength is significantly brighter than the wafer. Furthermore, coherent light sources can be used for this purpose. The use of laser sources may further guide the passage of substantially higher optical energies through the wafer and into the light detector 42 enable.

In addition to using an optical illumination device to enhance transmission, optical detection devices may also be suitably tuned to minimize stray light. For example, optical detectors may be used which only observe the area of the wafer being illuminated. The optical detectors may have angular recording characteristics that favor receiving light emanating from the light source rather than from the wafer. For example, the black body radiation emitted by the wafer tends to emanate in all directions from the wafer surfaces. By appropriately restricting the angular recording characteristics of optical detectors so that they tend to receive light traveling in the direction defined by the optical light source means, the ratio of emitted radiation to transmitted light can be reduced. Similar considerations may apply to the radiation of stray light from the heating lamps 24 be applied. The heating lamps 24 may generate radiation that is transmitted through the wafer or reflected at the back of the wafer, depending on where the lamps are located. If the system includes optical detectors that do not receive direct light paths from the lamps through the wafer or light paths that meet the condition for reflection reflection of light on the wafer, the stray light from the lamps can be greatly reduced.

In addition to optical illuminators and optical detectors, the system of the present invention may further comprise an optical filter which shields radiation outside of a wavelength range about the wavelength used for the transmission measurement. For example, this wavelength range can be defined by an interference filter.

In particular, when an incoherent light source, such as a tungsten halogen lamp, as a calibration light source 23 is used, it is desirable that the filter has good barrier properties outside the desired passband. Specifically, the incoherent light source can emit light that is modulated at all wavelengths, and as a result, the light detector can 42 receive an alternating signal, which resulted from a modulation at other wavelengths than those of the Filterdurchlaßbereichs. For example, in most non-passband applications, the filter transmission should be below about 10 ^-3 , and if measurements are made using wavelengths that are less than about 1.4 micrometers, the filter desirably has the above barrier characteristics, in particular the long wavelength side of the pass band because the silicon transmission is higher at longer wavelengths.

In one embodiment, the filter shield may be less than about 10 ^-6 . This type of shielding can be achieved by combining two interference filters in such a way that their combined shielding achieves the desired value. In some cases it can be convenient to put one of the filters before the radiation of the lamp source to limit the wavelength range which is emitted by the lamp.

When the calibration light source 23 however, as a coherent light source, such as a laser, no filters are needed since the range of modulated wavelengths is naturally narrow. Nevertheless, in one embodiment, a filter may be used to reduce the amount of scattered radiation from the wafer and the heating lamps.

Even if an incoherent light source is used, a filter may be undesirable. Alternatively, a multirange filter can be used. Working without a narrow range filter or with a multi-range filter can offer several advantages in some circumstances. For example, when operating without filters, a detector can be used to detect radiation from different light sources emitting radiation at different wavelengths without the need to change filters.

In a further embodiment of the present invention, the calibration light source 23 emit polarized light. In this embodiment, the system may include optical detectors that select a particular polarization to eliminate stray light. To generate polarized light, the calibration light source 23 a laser that is naturally polarized. Alternatively, the calibration light source 23 include a polarizer.

calibration wafers

The calibration wafer used in the system of the present invention is selected such that the transmittance of light through the wafer at the wavelength detected by the light detector 42 is observed, is a function of temperature. The wafer may be optimized for calibration in any number of ways, including changing the thickness, doping the wafer, applying surface coatings to the wafer, and modifying the surface texture.

In one embodiment, the calibration wafer may be a simple silicon wafer. The wafer may be a slightly doped silicon wafer having a resistivity greater than about 0.5 Ωcm. In this embodiment, wafers with a standard thickness can be used. Currently, standard wafer thicknesses are 725 microns for a 200mm wafer and 775 microns for a 300mm wafer. For most applications, the wafer is polished on both sides to improve the repeatability of the calibration standard.

The calculation of the temperature of the calibration wafer depends on the wavelength of the light transmitted through the wafer and the thickness of the wafer. In view of this, the thickness of the wafer should be known with some accuracy. In one embodiment, it may be desirable to make a correction for changes in wafer thicknesses used in temperature measurements. For example, the wafer thickness may be measured, and this data may be input to the algorithm used to determine the wafer temperature. Alternatively, the system of the present invention may be provided with an instrument which measures the wafer thickness and this information for use in temperature measurements, for example automatically to the controller, for example 50 transmitted. The wafer thickness instrument may measure the thickness of the wafer in the heat treatment chamber or may measure the thickness of the wafer prior to placing the wafer in the chamber. However, such an instrument is not necessary if the calibration wafer is made such that changes in thickness are negligible.

To the reflection of light coming from the calibration light source 23 is radiated to suppress the wafer, the calibration wafer 14 be coated in one embodiment with a reflection-damping coating. Coating the wafer with a reflection-damping coating not only reduces the amount of light that is reflected on the wafer, but also reduces the effect of the interference that occurs in the wafer.

In the 6 and 7 are two embodiments of a calibration wafer 14 which contains reflection-damping coatings. In 6 is a single reflection-damping coating 70 on the upper surface of the calibration wafer 14 available. In 7 In contrast, a reflection-damping coating 70 on the upper surface of the wafer 14 arranged while a second reflection-damping coating 72 is arranged on the underside of the wafer.

When reflection-damping coatings are applied to the wafer, the reflection of light at the infrared wavelength of interest can be significantly reduced, and interference effects are suppressed. The reflection-damping coating (or coatings) also has an advantage in that it increases the amount of light transmitted through the wafer, thereby improving the accuracy of the transmission measurements.

However, reflection damping coatings can affect the emissivity of the wafer at the pyrometer wavelength of the pyrometer being calibrated. For calibrations performed at high temperatures where the wafer is usually opaque at the pyrometer wavelength, it may be desirable to coat only one surface of the wafer, as in FIG 6 shown. Specifically, the surface of the wafer facing the pyrometer can remain uncoated so that the desired effect is achieved without affecting the emissivity at the pyrometer wavelength.

In another embodiment of the present invention as shown in FIG 8th can the calibration wafer 14 not just a reflection-damping coating 70 but also a coating 74 which has a certain radiating power. In particular, the temperature measuring device contained in the heat treatment chamber is calibrated in many situations with a group of wafers having different spectral emittance values at the pyrometer wavelength. Wafers with different radiation levels are used to correct for radiation effects in pyrometry and to make the temperature measurements independent of the spectral emittance of the wafer. As a result, in some embodiments, different calibration wafers having particular radiation values may be used in accordance with the present invention.

In general, any suitable reflection-damping coating according to the present invention can be used. Such coatings can be made, for example, of silicon dioxide, silicon nitride, or a combination of both. Such materials may also be used to form coatings having a certain emissivity. Silicon films can also be used for this purpose. Silicon films have a high refractive index, which may be useful in some applications. The coatings 70 respectively. 74 as shown in 8th can also be made from a dielectric film. The dielectric film may be a multilayer film which is specifically tuned to have the appropriate reflectivity and / or emissivity at the desired wavelength. Such films are known in the art and commercially available.

If present, the coating may be 70 respectively. 74 the transmission of the infrared light emitted by the calibration light source 23 is radiated, influence. These changes may be accounted for by calculations or measurements and included in the algorithm used to calculate the temperature of the calibration wafer. Furthermore, it is possible to form various coating designs which act as reflection-damping coatings at the infrared transmission wavelengths and which act as reflective or reflection-damping coatings at the pyrometer wavelength.

In addition to possibly improving the accuracy of temperature measurements made in accordance with the present invention, the use of anti-reflective coatings and other types of coatings may offer further advantages. For example, by choosing the optical properties of the coatings on the calibration wafer, it is possible to test various aspects of the operation of the temperature measurement system and to provide a diagnosis of the nature of the problem. For example, a test that checks whether the optical and electrical pyrometer devices are functioning properly may use a wafer back coating which is "black" at the pyrometer wavelengths so that the signal at the pyrometer will not be affected by other aspects of the optical system devices, such as by influences which are caused by multiple reflections between the wafer and the chamber walls. This is particularly useful when the system uses a reflection enhancement of the wafer emissivity to contribute to the independence of the emissivity. In these systems, the reflectivity of the auxiliary reflector, which is used to enhance the radiating power, plays a key role in the operation of the system. A test which can reveal if the reflectivity of the reflective plate has deteriorated uses a coating which is highly reflective at the pyrometer wavelength so that multiple reflections occur on the reflective plate. This type of wafer may also be used to check for correction systems for the radiating power in any kind of system will work, be useful. These test types can differentiate between different types of problems without requiring that the chamber be opened for inspection.

Coatings as described above can further help to reduce the effect of progressive heat degradation of the optical properties of the wafer due to oxidation and surface roughening. As a result, multiple heat cycles can be applied to the calibration wafer without degradation. For example, a thin oxide layer, such as a thickness of less than 30 nanometers, may protect the silicon surface from hot etching resulting from active oxidation by low concentrations of oxygen and water vapor in the ambient gas. A thin nitride film can serve a similar purpose. The films can be included as top layers in the series of coatings used for anti-reflection coatings or for changing the spectral emissivity as described above. Furthermore, by choosing oxide films that are less than about 30 nanometers thick, the influence of the film on the radiating power of the wafer can be minimized.

It should also be appreciated that other than using silicon wafers as calibration wafers, various other types of wafers may be used. In general, the calibration wafer can be made of any suitable material having a temperature-dependent transmission or a temperature-dependent reflection spectrum. For example, the calibration wafer may also be made of germanium, silicon carbide, gallium arsenide, aluminum arsenide, indium phosphide, gallium phosphide, gallium nitride, and alloys thereof. In fact, some of the above materials may be useful to extend the temperature range for radiation.

With respect to using silicon for the calibration wafer, it is known that silicon has good temperature transmission properties at temperatures less than about 850 ° C for standard thickness wafers. However, as described above, at temperatures above 850 ° C, silicon begins to absorb more light energy, making temperature measurements more difficult. In one embodiment, thinner wafers may be used to extend temperature measurements in accordance with the present invention to higher temperatures. For example, the predicted internal transmission at 1.5 micron wavelength for a 250 micron wafer at 950 ° C is 0.012, which is over 300,000 times greater than the transmission for a conventional 725 micron thickness wafer. By using very thin wafers, the infrared transmittance can be extended to higher temperatures. Furthermore, using thin wafers does not affect temperature measurements made by the pyrometer as long as the wafer remains opaque to radiation at the wavelength of the pyrometer.

However, various practical problems can arise when relatively thin wafers are used. For example, at high temperatures, the wafers may bend under their own weight and even be permanently deformed. The 9 to 18 are examples of various embodiments of calibration wafers having thin regions where these types of problems can be minimized.

For example, in 9 a calibration wafer 14 which has a thin area for transmission measurements. In this embodiment, the wafer comprises 14 a hole or a passage 80 at a location which is in the field of view or close to the field of view of the light detector 42 and the temperature measuring device or the pyrometer 27 which or which should be calibrated. In this embodiment, a silicon element 82 having the desired thickness at the top of the hole 80 arranged. The thickness of the silicon element 82 For example, it may be less than about 300 microns, especially less than about 200 microns, and more particularly less than about 150 microns. By arranging the silicon element 82 over the hole 80 which is in the wafer 14 is formed, a calibration wafer for use in heat treatment chambers, which is relatively strong but has a thin portion for use in making measurements, can be made in accordance with the present invention.

The silicon element 82 can be in position over the hole 80 and attached to the wafer using various methods. For example, the silicon element 82 in one embodiment, being mounted in position by an adhesive bonding method. Any bonding method, such as anodic or thermal bonding, may be used.

In an alternative embodiment, a retaining cap may be disposed over the wafer to hold the silicon element in position. The holding member may be made of silicon, silicon carbide, silicon dioxide (quartz) or sapphire. If the retainer cap is not transparent, in some applications it may be necessary to place a hole or passageway through the retainer cap which is disposed in alignment with the silicon element to make accurate transmission measurements. However, if a transparent material is used, such as quartz or sapphire, such an opening is not needed.

In one embodiment, the silicon element 82 have different thicknesses to cover different temperature ranges. In this embodiment, the variable thickness range may allow the system to use fewer infrared transmission wavelengths to calibrate in a wider temperature range. Further, if multiple pyrometers are to be calibrated, the calibration wafer may be used 14 many different holes in the many different places include, as in 13 shown. Alternatively, a group of different calibration wafers may be used, each containing a single or a few holes at selected locations.

As in 10 shown, the calibration wafer 14 in one embodiment, a recess 84 comprising a paragraph for the arrangement of the thin element 82 contains. In this embodiment, the thin element remains 82 placed in alignment during treatment and is easier to place on top of the wafer.

In another embodiment, rather than a hole in the calibration wafer 14 and then cover the hole with a thin member, a thin area in the wafer by forming a depression 86 be formed in the wafer, as in the 11 and 12 shown. As shown, through the depression 86 a thin section 88 in the wafer 14 educated. The wells 86 may be formed by any suitable technique, such as by machining or by etching. As in 14 shown, has the recess 86 in one embodiment, a stepped thickness which forms a frusto-conical shape. Furthermore, the corners can also be curved. The stepped thickness and curved corners reduce temperature gradients at the edges of the thin section, thereby reducing the possibility of mechanical interference and reducing stress.

When the calibration wafer comprises thin portions, there is a possibility that temperature gradients develop in the wafer upon heating. To reduce the effect of differences in thermal radiation properties between the thin portion and the remainder of the wafer, the wafer may include a coating. The coating may be, for example, a single layer or a multi-layer coating. The coating may be made of materials such as silicon dioxide, silicon, polysilicon and / or silicon nitride. The coating may be tuned to better match the radiation and absorbency of the thin and thick sections. In one embodiment, the coating may be made of any of the reflection-damping coatings described above.

In an alternative embodiment, the calibration wafer may comprise a filler disposed adjacent the thin section to reduce the thermal mass differences. The filling element may be made, for example, of quartz or alumina, such as sapphire.

Further exemplary embodiments of a calibration wafer produced according to the invention 14 are in the 16 . 17 and 18 shown. In these embodiments, the calibration wafer comprises 14 a light transmission area 90 which through a variety of channels 92 is defined. Thus, the transmission ranges include 90 thin areas and thick areas mixed, the thick areas having the same thickness as the wafer itself. The channels 92 can only pass through a portion of the thickness of the wafer, as in FIG 16 shown, or may run through the entire thickness of the wafer, as in the 17 and 18 shown. In the 17 and 18 are the thick areas 94 on a thin element 82 appropriate. Furthermore, in 18 the thin element 82 in a depression 84 arranged in the wafer 14 is trained. In the embodiments which in the 17 and 18 are shown, the thin element 82 for example, by an adhesive bonding method on the wafer 14 be attached.

In the embodiments which in the 16 . 17 and 18 are shown, when the calibration wafer is heated to relatively high temperatures, the light transmission is mainly through the channels 92 certainly. Therefore, the presence of the thick elements disturbs 94 the temperature measurements are not. This embodiment of the calibration wafer offers several advantages. For example, by keeping the thin portions narrow and mixed with the thick portions, problems of lateral side temperature gradients and thermal stresses can be reduced. Further, it may be simpler to use a pyrometer, a calibration light source, or a light detector in alignment with the transmission range 90 to arrange.

When the embodiments, which in the 16 to 18 In some applications, it may be desirable to know the relationship between the thick areas and the thin areas to correct for the presence of the thick areas during measurements. This ratio can be measured in any suitable manner. For example, the ratio may be determined using physical measurements, or the transmitted radiation flux, when the wafer is in a beam path, may be compared to that without the wafer by optical measurements. The latter measurement may be performed at any suitable wavelength at which the thick region is effectively opaque. The regions may be further prepared in advance with high accuracy, for example, by forming them using an optical lithography method or other similar technique. The methods of micromachining can be used to create suitable structures. The determination of the thickness of the thin regions can be achieved, for example, by conducting a transmission measurement at a known temperature at a suitable wavelength.

It should be noted that when a transmission area 90 is formed, the wafer may contain several areas, as in 14 or may include a single transmission area covering the entire wafer, as in FIG 15 shown.

When the calibration wafer is picked up, which in 17 respectively. 18 is shown, it may be cheaper to align the wafer so that the thin element 82 is reversed so that the thin element faces the pyrometer being calibrated. This arrangement may be advantageous because the pyrometer detects an opaque, homogeneous surface rather than an array of holes.

In 19 is another embodiment of a calibration wafer 14 shown. In this embodiment, the calibration wafer comprises 14 a thin silicon layer 100 which is on top of a transparent substrate 102 is arranged. For example, the transparent substrate may consist of aluminum oxynitride, spinel, silica or sapphire. The result is a solid calibration wafer that has the effect of a very thin silicon material.

The silicon layer 100 can be mounted on the transparent material in a number of different ways. For example, the silicon layer may be attached to the transparent material by an adhesive bonding method, or the silicon layer may be formed by deposition on the top of the transparent material.

In 20 is another embodiment of a calibration wafer 14 shown. In this embodiment, the calibration wafer comprises 14 a thin silicon layer 100 which are on top of a silicon substrate 106 is arranged. The silicon layer 100 is through an insulating layer 104 from the silicon substrate 106 isolated. The insulating layer 104 may be made of an oxide such as silicon dioxide. As illustrated, the calibration wafer comprises 14 also a transmission area 90 which channels 92 which is present in the silicon substrate 106 are formed.

In 21 is a similar embodiment of a calibration wafer 14 like that in 20 shown represented. In 21 are the channels 92 however, through the oxide layer 104 formed through.

In the embodiments which in the 16 . 17 . 18 . 20 and 21 are shown, a silicon wafer acts as a carrier for the transmission regions 90 , However, instead of being made of silicon, the carrier substrate may also be made of other materials. For example, in one embodiment, the substrate may be made of silicon carbide, offering advantages in terms of strength, high thermal conductivity, chemical resistance, and mechanical resistance.

In another embodiment of the present invention, the calibration wafer may comprise opaque areas made of a substantially opaque material and transmissive areas made of silicon, for example. This type of calibration wafer may be well suited for use in low temperature calibrations. In this embodiment, the pyrometer that is calibrated may be suitably arranged to detect heat radiation emitted by the wafer in the opaque regions. However, the permeability measurements can be made in the permeable areas.

Substantially opaque materials that can be used to construct the wafer include silicon doped with a material such as boron, arsenic, or phosphorus. Other examples of substantially opaque materials include metal films such as titanium films, cobalt films, nickel films, and tungsten films, and films made from metal silicides such as titanium silicide, cobalt silicide, nickel silicide, and tungsten silicide. Further, some other conductive materials such as titanium nitride may be used.

As mentioned above, in some applications it may be desirable to have the ratio between the thick and the thin regions of the transmission regions 90 to know. In one embodiment, however, it is possible that this information is not needed as long as the thick areas at the low temperature used in the infrared transmission method to normalize the signal are opaque. This arrangement eliminates the need for separate measurement because the method is self-correcting. The opacity can be measured by various methods. For example, in one embodiment, the normalization of the signal may be at a temperature for which it is known that the thick portions are opaque but the thin ones are completely transparent. Alternatively, a coating may be applied to the thick areas, the coating being highly absorbent or highly reflective at the selected test wavelength. Another technique is to heavily dope the thick areas, for example by ion implantation.

In one embodiment, the calibration wafer may be made primarily of a material that is opaque at the normalization temperature. The wafer may then comprise a thin coating of silicon, similar to the wafer used in 19 is shown. In this embodiment, the carrier wafer may be made of any suitable material that is opaque at the wavelength of interest, such as made from a heavily doped material.

In another embodiment of the present invention, various calibration wafers made of different materials may be used. Using different materials may allow more measurements to be made over a wider temperature range. The other materials that may be used include silicon carbide, aluminum nitride, gallium nitride or gallium phosphide. In particular, a material may be used to construct the calibration wafer, which is transparent to the infrared transmission wavelength but opaque to the pyrometer wavelength.

For purposes of illustration, a table is presented below which lists some practical temperature ranges at three suggested wavelengths and three suggested wafer thicknesses. In this embodiment, the heading "T low" means a practical lower temperature in the range for any given combination of wavelength and thickness, and the heading "T high" means the upper temperature limit for the same combination. The lower temperature limit was set by decreasing the temperature sensitivity in this embodiment. More specifically, the lower limit means the temperature at which the light signal is no longer at least 0.1% of its value per change by 1 ° C (denoted as sens (% / ° C)); changes. On the other hand, the upper limit was set at a point where the wafer became very opaque. In this embodiment, the high temperature range was at a point where the wafer was no longer transmitting light energy at a transmittance ratio of 10 ^-8 (1 part of 100,000,000). In the table this is indicated by "int trans". The wavelengths 1310 nm and 1550 nm were chosen because they are favorable for commercial light sources. The wavelength of 1200 nm was an arbitrary choice. Wafer thickness (microns) Wavelength (nm) 1200 1310 1550 T low T up T low T up T low T up 725 T (° C) 125 600 360 745 415 885 int trans 0.96 9.283 × 10 ^-09 0.943 1.08 × 10 ^-08 0.95 1.29 × 10 ^-08 sens (% / ° C) 0.1 14 0.1 15.6 0.1 15.9 100 T (° C) 250 975 425 1060 560 1160 int trans 0.93 1,192 × 10 ^-08 0.95 1.53 × 10 ^-08 0.93 1.37 × 10 ^-08 sens (% / ° C) 0.1 7.9 0.1 9.1 0.1 10.8 60 T (° C) 300 1085 460 1165 600 1250 int trans 0.92 1.536 × 10 ^-08 0.94 1.15 × 10 ^-08 0.93 1.53 × 10 ^-08 sens (% / ° C) 0.1 7 0.1 8th 0.1 9.5

calibration

In the following, various methods for carrying out the operation of the present invention will be discussed. For example, in one embodiment, a selected calibration wafer is placed in the heat treatment chamber. Then a calibration procedure is carried out. The prescription causes the wafer to be heated in a predetermined cycle of temporal temperature control while the required data is being acquired. An algorithm as described above interprets the transmission data with respect to wafer temperature and calculates parameters used to correct the pyrometer system so that the temperatures derived from the pyrometer system match those derived from the infrared transmission system. Of course, the system can be used other than for pyrometers for calibrating other temperature measuring devices.

A typical protocol may include a heating cycle or multiple heating cycles wherein the wafer is heated to a given temperature determined by the pyrometer system and held there for a fixed period of time while data is being taken before being heated to a second temperature , and so on. The regulation covers the temperature range for which calibration is to be carried out. The protocol may include a portion for a temperature at which the permeability of the wafer is known and in which it is not a highly temperature dependent function. This part of the regulation allows the infrared system to receive the transmission signal which is used to normalize the signals so that the effects of changes in the optical devices of the infrared transmission measuring system can be eliminated.

Further, if a coherent light source is used, that portion of the protocol may include a slow temperature increase associated with significant changes in the optical path lengths through the wafer. These changes change the conditions for optical interference between the light beams which are reflected at the upper and lower surfaces of the wafer and therefore result in a fluctuating transmission signal. The data acquisition system can collect this transmission data and then time average, so that the effect of the fluctuations is reduced. This approach may be useful for stages of the protocol which are performed under conditions where the wafer permeability is high enough that multiple reflections in the wafer are a factor.

An alternative type of regulation is to dynamically collect data during a heating and / or cooling schedule. In this case, the rate of temperature change must be sufficiently slow for there to be a negligible time delay between the output of the two measuring systems, and also for adequate signal averaging to reduce experimental noise. In this embodiment, when a wafer having thin portions is used, the heat reaction of the thin portions should be similar in relation to the thick portions.

It may also be useful in some applications to make a measurement using the radiographic system before placing the calibration wafer in the chamber. The ratio of the signal when the wafer is in position compared to that without wafer provides an estimate of the transmissivity of the wafer. For example, the measured transmission of the wafer may be useful to check whether the correct wafer has been inserted or to check the deterioration of the wafer. The transmission signal level, when no wafer is present, is also a useful indicator of the state of the optical system for transmission measurements.

In an alternative embodiment to the above method, more than one calibration wafer may be used, each of which may be automatically loaded into the treatment system. The multiple calibration wafers can serve different purposes. For example, different wafers having different characteristics may be placed in the heat chamber to allow for proper operation both in a high temperature range and in a low temperature range. For example, thin area wafers can be used for higher temperatures. Further, the wafers may include various coatings to allow the necessary calibrations for the pyrometer system to provide independent of radiating capability temperature measurements.

In one application of the system of the present invention, it may be desirable to calibrate the pyrometer system only at one or a few selected temperatures to quickly demonstrate that the system is operating properly. In this case, the calibration wafer may be loaded and a very simple procedure performed, for example, heating to a test temperature and collecting pyrometer and infrared transmission data. This procedure may be routinely performed at user-specified intervals. The data required for this process can be collected to track any bias tendency of the pyrometer system characteristics. If a noticeable divergence between the temperature measuring devices and the particular radiant temperature is observed, the system may be recalibrated or may undergo maintenance or chamber cleaning.

In some applications, the transmissivity measurement system of the present invention may also be operated during normal treatment of the wafers. Specifically, the system of the present invention may be used during normal wafer handling where wafer substrate doping is known and the wafer transmits a measurable amount of infrared radiation. For example, the procedure may be performed, and while the pyrometer is making temperature measurements, an algorithm tests the measurements from the pyrometer as compared to those from the infrared transmission. If the difference between the measured values exceeds a certain limit, this may be an indication that a corrective action is required. This procedure may be performed in part or all of the specified temperature range or time.

In fact, if enough information about the wafer being processed is known, the temperature measuring device in the treatment chamber can be calibrated while the real wafer is being treated. For example, the calibration may be in the early part of the temperature cycle, with the wafer still at a temperature that is low enough for the infrared transmission system to function properly. In this application, the temperature derived from the infrared transmission may serve to improve the estimate of the radiating power of the wafer and therefore to improve the accuracy of the pyrometer.

In one embodiment, the transmissivity measurement system of the present invention may be used to monitor the evenness of the process. In this embodiment, the system preferably includes a plurality of transmission measuring devices which may serve to measure light transmission at various locations on the wafer. During normal wafer handling or a test run using a particular wafer, the transmission measurement system can track the temperature of the wafer at the multiple locations. This information can then be used to check and determine if the heating cycle programmed for the system is functioning properly at all locations where a permeability measurement is made. More specifically, in this embodiment, the transmission measurement system provides a real-time method for proving that the heating cycles are properly set. For example, the transmissivity measurement system may determine the temperature profile of a heating cycle, including, for accuracy, heating and cooling rates. By keeping the heating cycles within predetermined limits at all the monitored locations, uniformity of operation is improved, regardless of whether the operation performed in the chamber is annealing or deposition of materials on a wafer.

In principle, the heating system of the heat treatment chamber may be controlled using feedback control based on the temperature derived by the infrared transmission measurement of the present invention in a closed loop mode. This may be useful in the event that the pyrometer has never been calibrated before and its measurements are therefore too inaccurate to allow it to be used to control the heating cycle.

Further, except for use in a control cycle, the infrared transmission transmittance measuring system of the present invention may be used in a no-feedback control cycle. In a no feedback control cycle, no feedback signal is used to control the light sources. Instead, the light sources are appropriately pre-programmed to perform a particular heating cycle.

Use of the transmissivity measuring system of the present invention to determine the temperature of wafers independently of any other temperature measuring device is particularly useful at temperatures less than about 800 ° C, at which most wafers transmit a measurable amount of infrared radiation. In this embodiment, the radiographic system of the present invention may be used to monitor the temperature of the wafer being treated at lower temperatures, while the normal temperature measurement system may be used to monitor the temperature of the wafer at higher temperatures. For example, in this embodiment the transmissivity measurement system is particularly well suited for use in conjunction with pyrometers which are not adequately accurate at lower temperatures.

Lastly, full return control can be applied throughout the entire treatment cycle from room temperature upwards, eliminating the need for a hot block with open loop control, which is normally used to heat a wafer to the temperature at which pyrometer control occurs. This embodiment can improve overall process control and processing while reducing the effort required to develop regulations. Further, in applications where the maximum treatment temperatures are lower than about 800 ° C, the entire heating cycle should be controlled by the transmissivity measurement system of the present invention.

The presence of a localized transmission measurement system may also provide various other useful information during the processing of wafers. For example, the system of the present invention is further adapted to provide information as to whether or not the wafer being treated is opaque at the temperature of interest. This information can be used to automatically select optimal temperature measurement and control algorithms for treating lightly doped, heavily doped and metallized wafers in optimal ways that take into account their very different energy absorption properties.

Claims (70)

Method for calibrating a temperature measuring device ( 27 ), comprising: emitting light energy from a calibration light source ( 23 ) on a wafer ( 14 ), which is made of a semiconductor material, while the wafer ( 14 ) is heated; Detecting the radiated amount of light energy passing through the wafer ( 14 ) is allowed through; Determining the temperature of the wafer ( 14 ) based on the amount of transmitted light energy detected; and calibrating the temperature measuring device ( 27 ), which determines the temperature of the wafer ( 14 ) based on the temperature determined by the amount of light energy passing through the wafer ( 14 ) is determined. The method of claim 1, comprising: providing a heat treatment chamber ( 12 ), which at least one temperature measuring device ( 27 ) for monitoring the temperature of a semiconductor wafer which is in the chamber ( 12 ), wherein the heat treatment chamber ( 12 ) in conjunction with a heating device ( 22 ) for heating wafers ( 14 ), which in the chamber ( 12 ), the chamber ( 12 ) the calibration light source ( 23 ); and Arranging the calibration wafer ( 14 ) in the heat treatment chamber ( 12 ). Method according to claim 2, wherein the heating device ( 22 ) at least one light energy source ( 24 ). Method according to claim 2, wherein the heating device ( 22 ) a susceptor plate ( 26 ). Method according to claim 2, wherein the light energy generated by the calibration wafer ( 14 ) is detected at a predetermined wavelength. The method of claim 5, wherein the predetermined wavelength comprises a wavelength of about 1 micron to about 2 microns. The method of claim 2, wherein the calibration wafer ( 14 ) comprises a silicon wafer. Method according to claim 2, wherein the temperature measuring device ( 27 ) comprises a pyrometer. Method according to claim 2, wherein the amount of light energy generated by the calibration wafer ( 14 ) is passed through at one location on the wafer ( 14 ), in which the thickness of the wafer ( 14 ) is less than about 150 microns. Method according to claim 9, wherein the amount of light energy generated by the calibration wafer ( 14 ) is passed through at one location on the wafer ( 14 ), in which the thickness of the wafer ( 14 ) was reduced. Method according to claim 2, wherein the calibration light source ( 23 ) comprises a laser or a light emitting diode. Method according to claim 2, wherein the calibration light source ( 23 ) comprises a super-luminescent LED. Method according to claim 2, wherein the calibration light source ( 23 ) comprises a superfluorescent fiber laser or a semiconductor laser. Method according to claim 5, wherein the light energy generated by the calibration wafer ( 14 ) is detected at more than one wavelength. The method of claim 2, wherein the calibration wafer ( 14 ) a wafer ( 14 ), which has at least one thin region, the thin region having a first thickness which is smaller than a second thickness of the wafer (US Pat. 14 ), the thin region having a thickness of less than about 150 microns. The method of claim 2, wherein the thin region has a thickness of less than about 100 micrometers. The method of claim 15, wherein the wafer ( 14 ) comprises a plurality of thin regions. The method of claim 15, wherein the calibration wafer ( 14 ) further comprises a coating ( 70 . 72 . 74 ), which on at least one side of the wafer ( 14 ) is arranged. The method of claim 18, wherein the reflectivity of the coating ( 70 . 72 . 74 ) at a particular wavelength is less than about 0.25 with the particular wavelength being between about 1 micron and 2 microns. The method of claim 15, wherein the wafer ( 14 ) comprises a plurality of thin regions arranged in groups. The method of claim 20, wherein the wafer ( 14 ) comprises a plurality of locations in which the plurality of thin areas has been grouped together. The method of claim 15, wherein the thin region has a maximum elongation of at least 1 mm. The method of claim 15, wherein the calibration wafer ( 14 ) an opening ( 80 ), wherein the thin region is a thin element ( 82 ), which over the opening ( 80 ), wherein the calibration wafer ( 14 ) further comprises a holding cap which on one side of the wafer ( 14 ) is arranged around the thin element ( 82 ) to hold in position. A method according to claim 23, wherein the retaining cap comprises a material which, at a particular wavelength, at which the light energy passing through the calibration wafer ( 14 ), is detected, is transparent. The method of claim 15, wherein the calibration wafer ( 14 ) further comprising a filler disposed adjacent to said thin region, said filler being made of a material which is transparent to a wavelength of light at which said radiation is detected, said filling element serving to control the thermal mass differences between said light source thin area and the rest of the wafer ( 14 ). The method of claim 25, wherein the filler is made of quartz or alumina. Method according to claim 2, wherein the amount of light energy generated by the calibration wafer ( 14 ) is detected at multiple wavelengths, the detected light energy at the plurality of wavelengths being used to determine the temperature of the calibration wafer (Fig. 14 ). Method according to claim 2, wherein the heat treatment chamber ( 12 ) in conjunction with a first calibration light source ( 23 ) and a second calibration light source ( 23 ), the first calibration light source ( 23 ) comprises an incoherent light source, the second calibration light source ( 23 ) comprises a coherent light source, the first calibration light source ( 23 ) is used to make transmission measurements at lower temperatures and the second calibration light source ( 23 ) is used to measure the temperature of the wafer ( 14 ) at higher temperatures in conjunction with the lower temperature transmission measurements. The method of claim 23, wherein the retaining cap is not continuously over the surface of the wafer ( 14 ), wherein the retaining cap is not at the location on the wafer ( 14 ), where the temperature measuring device ( 27 ) the temperature of the wafer ( 14 ) certainly. The method of claim 15, wherein the calibration wafer ( 14 ) a coating ( 70 . 72 . 74 The coating serves to control the effects of differences between the thin regions and the remainder of the wafer. 14 ). The method of claim 30, wherein the coating ( 70 . 72 . 74 ) Silicon, polysilicon, silicon nitride or mixtures thereof. The method of claim 2, wherein the calibration wafer ( 14 ) a wafer ( 14 ), which is made of an opaque material, wherein the wafer ( 14 ) further comprises transmission regions comprising silicon, the transmission regions being coated, where the amount of transmitted light energy is detected. The method of claim 32, wherein the opaque material comprises doped silicon, a metal or a silicide. The method of claim 1, wherein the radiated light energy comprises electromagnetic radiation having a predetermined wavelength. The method of claim 34, wherein the predetermined wavelength comprises a wavelength of about 1 micron to about 2 microns. Method according to claim 1, wherein the temperature measuring device ( 27 ) comprises a pyrometer. The method of claim 1, wherein the amount of light energy passing through the wafer ( 14 ) is passed through at one location on the wafer ( 14 ), in which the thickness of the wafer ( 14 ) is less than about 150 microns. The method of claim 1, wherein the amount of light energy passing through the wafer ( 14 ) is passed through at one location on the wafer ( 14 ), in which the thickness of the wafer ( 14 ) in relation to the remainder of the wafer ( 14 ) was reduced. Method according to claim 1, wherein the wafer ( 14 ) comprises a silicon wafer. Method according to claim 1, wherein the wafer ( 14 ) comprises at least one thin region having a first thickness which is smaller than a second thickness of the wafer (US Pat. 14 ), the thin region having a thickness of less than about 150 microns. The method of claim 40, wherein the thin region has a thickness of less than about 100 micrometers. Method according to claim 1, wherein the wafer ( 14 ) a coating on at least one side of the wafer ( 14 ) having. The method of claim 42, wherein the coating ( 70 . 72 . 74 ) at a particular wavelength has a reflectivity of less than about 0.25, the particular wavelength being between about 1 micron and 2 microns. The method of claim 40, wherein the wafer ( 14 ) comprises at least 2 areas. Method according to claim 1, wherein the calibration light source ( 23 ) comprises a coherent light source which is arranged in suitable connection with an optical element, said optical element comprising a ground glass material. System ( 10 ) for calibrating a temperature measuring device ( 27 ) in heat treatment chambers ( 12 ), comprising: a chamber ( 12 ), which is suitable semiconductor wafers ( 14 ); a heating device ( 22 ) in conjunction with the Chamber ( 12 ) for heating a semiconductor wafer which is in the chamber ( 12 ) is included; a temperature measuring device ( 27 ) for monitoring the temperature of semiconductor wafers ( 14 ), which in the chamber ( 12 ) are included; a calibration wafer ( 14 ) for placement in the chamber ( 12 ); a calibration light source ( 23 ) for radiating energy at at least one specific wavelength onto the calibration wafer ( 14 ); and a light detector ( 42 ), which is suitably arranged to control the amount of light energy passing through the wafer ( 14 ) is passed from the calibration light source ( 23 ) at the specific wavelength, the amount of light energy detected being used to measure the temperature measuring device ( 27 ) to calibrate. The system of claim 46, further comprising a controller ( 50 ) in conjunction with the light detector ( 42 ) and the temperature measuring device ( 27 ), whereby the controller ( 50 ) is configured to receive information from the light detector ( 42 ) and to use the information thereafter to heat the temperature measuring device ( 27 ) to calibrate. A system according to claim 46, wherein the heating device ( 22 ) at least one light energy source ( 24 ). A system according to claim 46, wherein the heating device ( 22 ) a susceptor plate ( 26 ). A system according to claim 46, wherein the light detector ( 42 ) comprises a photosensor. A system according to claim 46, wherein the temperature measuring device ( 27 ) comprises a pyrometer. A system according to claim 46, wherein the light detector ( 42 ) is adapted to detect the light energy comprising electromagnetic radiation having a wavelength of from about 1 micron to about 2 microns. A system according to claim 46, wherein the calibration light source ( 23 ) comprises a laser, a light emitting diode, a super luminescent light emitting diode or a superfluorescent fiber laser. Calibration wafer ( 14 ), which is intended for calibrating temperature measuring devices ( 27 ) in heat treatment chambers ( 12 ), the calibration wafer ( 14 ) comprises: a wafer ( 14 ) with a diameter of at least 200 mm, the wafer ( 14 ) comprises at least one thin region having a first thickness which is smaller than a second thickness of the wafer (US Pat. 14 ), wherein the thin region has a thickness of less than 150 microns, the thin region being a thin piece of material ( 82 ), which over a hole ( 80 ), which passes through the wafer ( 14 ) is defined. The calibration wafer of claim 54, wherein the thin region has a thickness of less than about 100 micrometers. Calibration wafer according to claim 54, wherein the wafer ( 14 ) comprises at least two thin regions. Calibration wafer according to claim 54, wherein the second thickness of the wafer ( 14 ) is at least 250 microns. The calibration wafer according to claim 54, wherein the thin region has a maximum elongation of at least 1 mm. The calibration wafer according to claim 54, wherein the specific resistance of the thin region is at least 0.01 Ωcm. The calibration wafer of claim 54, wherein the thin region comprises silicon. Calibration wafer according to claim 54, wherein the wafer ( 14 ) is made of silicon. Calibration wafer according to claim 54, wherein the wafer ( 14 ) a coating ( 70 . 72 . 74 ) on at least one side of the wafer ( 14 ). Calibration wafer according to claim 62, wherein the reflectivity of the wafer ( 14 ) at a particular wavelength is less than about 0.25 with the particular wavelength being between about 1 micron and 2 microns. The calibration wafer of claim 54, wherein the thin region is surrounded by walls, the walls having an inclined surface. Calibration wafer according to claim 54, wherein the wafer ( 14 ) comprises a plurality of thin regions arranged in groups. Calibration wafer according to claim 54, wherein the wafer ( 14 ) comprises a plurality of locations in which the plurality of thin areas has been grouped together. Calibration wafer according to claim 54, wherein the calibration wafer ( 14 ) an opening ( 80 ), wherein the thin region is a thin element ( 82 ), which over the opening ( 80 ), wherein the calibration wafer ( 14 ) further comprises a holding cap which on one side of the wafer ( 14 ) is arranged to hold the thin element in position. The calibration wafer of claim 67, wherein the holding cap comprises a material which is exposed at a predetermined wavelength at which the light energy is detected by the calibration wafer (10). 14 ) is transparent. Calibration wafer according to claim 54, wherein the calibration wafer ( 14 ) further comprises a filling member disposed adjacent to the thin region, the filling member being made of a material which is transparent to light at a wavelength at which the transmission is detected. The calibration wafer of claim 69, wherein the filler element is made of quartz or aluminum oxide.

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